The modes of endocrine therapy for advanced breast cancer include ovariectomy, adrenalectomy, hypophysectomy and administration of androgens, estrogens, progestogens or adrenocortical steroids. The success or failure of a given treatment regimen is thought to depend in part on the quantities and characteristics of specific hormone-binding components or receptors in the tumors. Many laboratories are studying estrogen receptors, but little emphasis has been placed on receptors for other steroids which influence tumor growth. We propose to identify and discriminate among receptors for each group of steroids in human breast tumors and their metastases, and to compare them with steroid-binding components in normal breast, breast cyst fluid and serum. Extracts of specimens will be incubated with different H3-steroids, with or without competing unlabeled steroids or analogs. The resultant macromolecular complexes will be analyzed primarily by polyacrylamide gel electrophoresis, using procedures refined in this laboratory. This method separates steroid-receptor complexes that cannot be resolved by density gradient centrifugation or other techniques that depend only on molecular size. The improved resolution permits evaluation of the specificity, affinities and binding capacity of each receptor species. In pilot experiments, we have detected distinct binding components for dihydrotestosterone and cortisol in human breast tumors. This method will be incorporated into a protocol for clinical screening of steroid receptors in prostatic and uterine tumors as well as breast. Electrophoretic findings will be correlated with clinical, pathological and other biochemical data, to test the hypothesis that receptor assays are useful in the prognosis and treatment of potentially hormone-responsive cancers.